Much or most of what you know about health, nutrition, and medical practice is already obsolete, but it can take years for new information to be accepted by doctors, hospitals and, God knows, the government.
It's a truism that all knowledge is transient. I sometimes catch myself thinking "I can't believe they used to believe...." before I call myself on it and realize that in fifty years people will be saying that about us.
Dr. Semmelweiss possibly did more for women than any other person in history, or at least in medical history. He is a stand-out in the medical pantheon, but acceptance of his ideas was extremely slow and he was thought a nut and a crank by the medical establishment.
His life was a sad one, and short. I suspect he died of neurosyphilis, known then as General Paresis of the Insane. He might have gotten syphilis from the many prostitutes he tended to, or from prostitutes who tended to him.